Field: The invention is in the field of machine tools, particularly machine tools which utilize a tracer stylus or machine tools which utilize electronic control.
State of the Art: Profiling machine tools which utilize a tracer stylus are well known. An operator positions a pattern, which is an actual part, prototype of a part, or mock-up of a part, adjacent to the stylus and then uses the stylus by holding it against such pattern manipulating it in such a way to cause the feed table and milling spindle of the machine to move and mill from raw material a new part that is an exact copy of the pattern. Current tracer stylus systems utilize hydraulic control of the milling machines and the tracer styluses are expensive, precision hydraulic instruments using hydraulic spooler valves in the stylus assembly to control the hydraulic valves which operate the hydraulic rams to position the feed table and milling spindle. Each of these hydraulic stylus assemblies cost between $17,000 and $20,000 and require a very experienced operator to make the necessary mechanical adjustments and to satisfactorily operate the system, particularly in connection with making complex parts. Further, such hydraulic stylus assemblies are usable only with hydraulically operated machine tools, and not with the newer electrically operated tools.
Most of the newer machine tools are computer controlled so that when the computer is properly programmed, the tool automatically mills the desired part. However, in most cases the time and cost of developing a program for a particular part can be substantial. While such automatic operation is beneficial for a large run of parts where the programming cost can be spread over the large number of parts made, the programming costs become prohibitive when a limited run is necessary or a single replacement part is made.
In addition, in such computer-controlled systems, the movement of the spindle and raw material is generally done electrically rather than hydraulically, although some hybrid systems are available which provide electrical control of the hydraulic systems.
There is one computer-controlled milling machine currently on the market, made by Getty Machine Tool Division of Getty Oil, which incorproates a tracing stylus. With this machine, the stylus is connected directly to the computer of the control system and operates through the computer. The stylus is compatible only with the companion computer-controlled equipment and cannot be used with other equipment.
There is a need for a simple tracing stylus which produces electrical rather than hydraulic control signals so as to be compatible with electrically driven machine tools or electrically controlled, hydraulically driven machine tools, and which operates such tools directly, rather than through a computer system. With such operation, the tracing units would be compatible with a large number of existing machine tools whether or not computer controlled, and if computer controlled, the tools would not be dependent on the computer and could be operated even when the computer is shut down or is being repaired. Further, it would be advantageous to be able to use a stylus arrangement to trace a pattern and to program an associated computer through such tracing operation. In addition, a tracing stylus is needed that is simple to operate and adjust, with practically any operator being able to satisfactorily operate the machine tool, rather than requiring a highly experienced operator.